1. Field of the Invention
The present invention is directed to a method for the holographic recording of data which is in the form of electrical signals which signals are used to pulse modulate an object wave which is recorded with a coherent reference wave to produce hybrid holograms on a moving light-sensitive storage medium.
2. Prior Art
In order to achieve invariance in response to translation of a reconstructed image point at right angles to the storage plane, it has been suggested in the U.S. Pat. No. 3,809,453 to use astigmatic reference and object waves which have focal lines which are the same distance from the one-dimensional hologram and extend parallel to the storage plane in a direction at right angles to the direction of movement of the storage medium. In this case, the one-dimensional holograms are sequentially recorded in different parallel tracks of the tapelike storage medium with the tracks extending in the direction of movement or feed of the storage medium and being spaced apart in a direction extending perpendicular to the direction of movement.
For read-out of the stored one-dimensional holograms and in order to reconstruct the information stored therein, the storage medium is conducted past a reference light source which directs a light beam onto the storage medium and the cross section of the beam is equal to the size of the individual holograms. The light beam must be conducted over the storage medium at right angles to the direction of the tape feed in order to scan the various hologram tracks. If the read-out or reconstruction light beam does not precisely overlap the one-dimensional hologram, a noticeable signal fading occurs which is due to the widening of the optically reconstructed signal which widening is caused by diffraction and this misalignment also leads to less energy being available in the reconstructed beam.